In many public buildings, the heating, ventilation and air conditioning (HVAC) requirements are handled by a HVAC system which is automatically controlled by a pneumatic control system. In addition to those buildings having HVAC systems which are primarily controlled by a pneumatic system, other buildings may have an HVAC system which is electronically controlled, but may also have a pneumatic system as a back-up.
In the typical pneumatically controlled HVAC system, pneumatic signals are formed by changing the pressure of the air within tubes which interconnect the various components. A variety of sensing devices, such as a pneumatic transmitter or thermostat, send pneumatic input signals along the interconnecting or connecting tubes to a receiver controller. In dependence on these pneumatic signals, the receiver controller outputs one or more pneumatic signals which are, in turn, relayed to controlled valves which control the components of the air-handling system. The components typically being dampeners, fans and chilled and hot water supply or return valves.
One of the drawbacks of the pneumatic control system is the difficulty in determining in which component the problem may be when the HVAC system is not functioning properly. For example, when the chilled water valve is not operating the problem may be in the pneumatic transmitter or thermostat, the receiver controller or the chilled water valve. To pneumatically isolate the individual components may require the locating and tapping of the pneumatic connecting tubes leading to and from the component. This locating and tapping is time consuming. Compounding this drawback is that to isolate the receiver controller to check the controller may require a complete shutdown of the HVAC system.
A related drawback is that when the pneumatic control system is not functioning properly, to switch to a manual control of the HVAC system may require the location of a maintenance person who then activates the manual control by bypassing the receiver controller, thus causing a delay before the HVAC system is properly functioning.
Another drawback of the pneumatically controlled HVAC system is the calibration of the receiver controller, which requires the application of known inputs to the receiver controller to determine whether the controller is operating properly. To isolate the receiver controller for calibration also may require a shutdown of the system. These shut-downs may be costly and uncomfortable for the occupants of the building.
An additional drawback in the calibration of the receiver controller is the wear and tear on the connecting tubes which lead to the receiver controller. During the calibration process, the connecting tubes must be disconnected and replaced by tubes from the calibration device. After the calibration, the connecting tubes must be reconnected. The connection and reconnection of the connecting tubes cause wear on the tubes which may cause the tubes to fail and be replaced.
It is therefore an object of the present invention to provide a device which isolates the receiver controller from the components of the HVAC system without requiring a shutdown of the system.
Another object of the present invention is to provide a device which isolates the receiver controller and allows manual control of the HVAC system. A related object of the present invention is to provide a device which allows for the receiver controller to be calibrated while the HVAC system is operating under manual control.
A further object of the present invention is to provide a device which allows the connection and disconnection of the calibration device to the receiver controller without requiring the disconnection and reconnection of the tubes normally connected to the receiver controller.
A further object of the present invention is to provide a device which automatically will actuate a manual control of the HVAC system when a problem with the pneumatic control system is detected.